Question 7 from the first paper of 2004 asked the candidates to "outline the potential advantages and disadvantages of a tracheostomy in the weaning of patients from mechanical ventilation." This would be a gift if it were to ever appear again, but it never has. Additionally, Question 7 from the first paper of 2001 asked about aspiration in a patient with tracheostomy, and how one might go about detecting that (blue feeds were expected as a part of the answer).
A somewhat dated article by Charles Durbin seems to be a good resource for this, for various reasons but largely because it is frequently cited and because it was published in 2005 one can generally assume that it represents the state of the tracheostomy thinking during that period. Also, because it's old you can be sure the examiners have probably read it at some point. And it comes up often during Google search results, which means that modern day examiners will come across it as they write their SAQs. Another excellent resource is a 2007 review article by Paul De Leyn.
Since 2005 the literature has produced a few game-changing pieces of evidence, and so Durbin's recommendations for treatment cannot be used for exam revision in the modern era; however the physiological discussion and the list of advantages and disadvantages is worthy of respect. It has informed much of the ensuing discussion. As for the "modern" approach to the issue of when and how to offer tracheostomy, the balance of the evidence is discussed in the chapter on the indications and contraindications for this procedure.
Advantages of tracheostomy
Improved patient comfort
- Decreased sedation requirement: tracheotomised mechanically ventilated ICU patients require much less intravenous sedation (Nieszkowska et al, 2005). The reason for this is the reduced stimulation of their gag reflex and the loss of the constant irritation of delicate vocal cord structures which is extremely uncomfortable (Grap et al, 2002).
- Enhanced ability to communicate: not only is the reduced sedation requirements make communication easier, but the lack of oral tubing allows the patient to mouth words, allowing lip-reading. Not to mention the possibility of letting the cuff down occasionally, and letting the patient speak with a Passy-Muir valve.
- Improved positioning and mobility: the lack of heavy sedation makes it easier for these patients to be sat out in a chair, which not only improves their comfort but also their respiratory mechanics.
Avoidance of orotracheal tube-related complications
- Less vocal cord damage: We know that the duration of endotracheal intubation correlated with the risk of laryngeal damage which ranged from ulceration to vocal cord paralysis lasting several weeks. (Santos et al, 1994). An excellent review of the laryngeal complications of intubation by Colice et al (1989) has an excellent illustrative diagram, which I have stolen shamelessly:
- Less risk of laryngeal stenosis - due to scarring in the glottic posterior commissure between the arytenoid cartilages (Hawkins et al, 1980).
- Better recovery of voice quality - people tend to be hoarse following intubation, and the hoarseness is worse with prolonged intubation. The major cause of long term hoarseness seems to be cord paralysis and the formation of granulomae at the ulcerated edges of the vocal cords.
- Less damage to the tongue and lips from the endotracheal tube, which causes pressure areas and oedema of these structures.
Improved mechanics of ventilation
- Lower resistance to air flow - this has been established experimentally by Davis et al (1999) who studied twenty patients who failed extubation and required tracheostomy. Measurements of functional respiratory variables were made before and after tracheostomy. Airway resistance decreased by ~ 33%
- Decreased work of breathing - again, Davis et al (1999) found that among their cohort the work of breathing decreased by 50% on average.
- Decreased apparatus dead space is usually quoted as one of the advantages of tracheostomy, as the normal trachea has a volume of about 75ml, whereas the tracheostomy tube has about 5ml. The diagram below (stolen from from Pierson et al, 2005) demonstrates this:
However, we are not comparing tracheostomy to normal tracheas, but rather to an endotracheal tube. The difference between the volume of a normal ETT and a normal tracheostomy tube is less than 20ml, which is probably why the change in dead space does not contribute very much to the improvement of ventilation mechanics (Mohr et al, 2001).
- Improved respiratory function parameters: Lim et al (2015) found that the tidal volume, rapid shallow breathing index and the MEP/MIP values all improved following tracheostomy in a prospective cohort of difficult-to-wean patients.
- More rapid weaning from mechanical ventilation is a widely held belief which has been difficult to demonstrate experimentally, but which seems to have some support in the evidence. For instance, famous studies of early vs late tracheostomy (eg. Koch et al, 2012) found that the early group was weaned from ventilation almost 30% faster, suggesting that having a tracheostomy offers an advantage. This advantage has to be at least partially related to the fact that less sedation is required.
Advantages in airway care and secretion control
- Lower incidence of tube obstruction: the tracheostomy has an inner cannula which can be removed and exchanged or cleaned. The ETT, however, just ends up being caked with ungodly filth.
- Better oral hygiene because the ETT is a major obstacle to brushing teeth, etc. Once the tracheostomy is in situ, the patient can brush their own teeth.
- Better clearance of secretions by suctioning is often mentioned as an advantage of tracheostomy, but is difficult to find evidence for. Possible explanations for better secretion clearance by tracheostomy include a shorter tube length and therefore a reduced distance for secretions to travel on their way out (i.e. when the patient is coughing without the suction module attached).
- Lower incidence of VAP is quoted as an advantage of tracheostomy, but this does not seem to have strong evidence behind it either. Or rather, the evidence is contradictory. Nseir et al (2007) were able to demonstrate a decreased rate of VAP in their case-control study, but Terragni et al (2010) were not able to find much of a benefit in their small RCT.
Advantages for upper airway function
- Better preservation of swallowing is mentioned by Durbin (2005), but does not seem to be backed up by any evidence. Goldsmith (2000) reflects that both ETT and tracheostomy have a similar effect on swallowing function. The preservation of the gag reflex is one potential advantage, as it is not constantly triggered by the presence of a big piece of plastic in the posterior pharynx.
- Earlier oral feeding should be mentioned as possibility, but mainly to contrast with endotracheal intubation, where oral feeding is not a possibility. With the tracheostomy, at least you have the option (even though it may not be practical to go with this).
- Preservation of "glottic competence" can be described more directly as "big thing is no longer wedging the vocal cords in an open position". Obviously, the glottis cannot close when the ETT is in situ, and all responsibility for defence against aspiration falls upon the endotracheal tube cuff, which is far from impermeable. Ergo, in the absence of an ETT the vocal cords have the opportunity to close and prevent aspiration. This is obviously not perfect after prolonged intubation: Shaker et al (1995) demonstrated that the vocal cords are still fairly uncoordinated even with a tracheostomy.
- Decreased aspiration risk is the upshot of the abovementioned enhanced glottic competence. In essence, it is believed that in the presence of a tracheostomy the patient can close their glottis and will therefore be less likely to inhale upper airway secretions and vomit into the subglottic regions. However, they still aspirate, particularly if they are elderly (Eplern et al, 1994)
- Less skilled insertion: If the tracheostomy is well-established and the tract has matured, it can be re-inserted easily by relatively mindless carers. One recalls a respected senior surgeon recommending to a patient that they "wash it under the tap and stick it back in", which may not reflect the gold standard of care but illustrates the point nicely.
- Less skilled care: the daily maintenance of a well-established tracheostomy requires less skill than the care of an endotracheal tube, and so ICU-level care may not be required for such patients (in fact families may be counted upon to look after these people at home)
- Deferral of difficult conversation: the practice of protecting the patient from harmful or futile therapies occasionally becomes subsumed by the need to protect the intensivist from angry families. In order to avoid having to take an adversarial position, the lazy solution is to perform a tracheostomy, rapidly wean ventilation and discharge the persistently unconscious patient into the care of their ward team, thereby shifting the emotionally and ethically complex workload out of ICU.
- Prolongation of life: In spite of the fact that most people would react to long-term ventilation with "not me" and "fuck that", studies have shown that among neuromuscular disease patients receiving long-term domiciliary ventilation via tracheostomy 84% think that they have made the right choice, and 66% are satisfied with their lives in spite of significant financial stresses (this was a small American study by Narayanaswami et al, 2000). The authors were forced to conclude that "the physician's perception of a patient's poor quality of life on assisted ventilation is a major reason for discouraging assisted ventilation".
Disadvantages of tracheostomy
Disadvantages related to safety and complications
- The complications of the percutaneous and surgical tracheostomy procedure are discussed in greater detail elsewhere; it suffices to say that cutting somebody's throat and shoving a great big thing into it is not a benign procedure, and has a nonzero complication rate.
- Potential for dislodgement in an agitated patient or with clumsy carers is a major issue in patients who remain dependent on ventilation, and in patients whose tract has yet to mature. Particular risk factors include obesity, neck oedema, attachment to short or inflexible tubing and the use of a tracheostomy which is poorly sized for a given depth of pre-tracheal tissue.
- Humidification is inadequate; in the non-ventilated patient a HME ("Swedish nose") may be required, particularly if the patient is still requiring supplemental oxygen. That gas is hellishly cold and dry, and one does not wish to administer it directly to the tracheal mucosa.
- Passive humidifiers increase the work of breathing: the HME adds to dead space and airway resistance, negating some of the positive effects of tracheostomy on the work of breathing (Manthous et al, 1994)
- Blockage with secretions: even though there is an inner cannula, the tracheostomy can block. This is particularly likely if the patient has been liberated from the humidified circuit. With little humidification and in the absence of regular suctioning inspissated secretions can block the tube.
Disadvantages related to care for the artifical airway
- Complication of emergency airway management: if a patient with a tracheostomy loses their airway, the management is not straightforward. Bag-mask ventilation becomes problematic (the tracheal stoma will let the air out). Attempts to reinsert a dislodged tracheostomy are unlikely to be successful if the tract is immature, and intubation "from the top" will be required, with potential for injury and subcutaneous emphysema.
- Skilled care is still required: for instance, many nursing homes will not accept a patient with a tracheostomy. Family members should be willing to take such a patient home, and understand that specialised equipment for suctioning and humidification may be required.
- Failure to wean despite tracheostomy: if the tracheostomy does not contribute to weaning, the patient may become ventilator-dependent in a permanent way, which may not be viewed as a satisfactory outcome by patients or their families. This is obviously an individual issue (as is mentioned above, many long-term ventilated patients feel that they made the right decision in taking that option).
- No mortality benefit: studies seem to disagree, but the broad trend seems to be in the direction away from mortality benefit. Prospective cohorts have shown that there seems to be better in-ICU survival (Frutos-Vivar et al, 2005) but the study design allowed bias because intensivists could select patients in whom tracheostomy was inevitable. In contrast, Clec'h et al (2007) observed that "tracheostomy does not seem to reduce intensive care unit mortality when performed in unselected patients but may represent a burden after intensive care unit discharge." Furthermore, patients who were discharged from ICU (off the ventilator but still with tracheostomy in situ) actually had increased mortality.
- Dissatisfaction of the survivors: even people who end up being decannulated are generally less satisfied with their quality of life (Gilony et al, 2005). Studies of long term ventilated patients with tracheostomies are frequently done on patients suffering from a long and chronic disease (eg. Duchenne muscular dystrophy) whose acceptance of diminished function develops gradually over years. Many tracheostomy patients discharged from the ICU are instead previously well people who have had some sort of acute disabling illness or trauma. These patients may be less accepting of their diminished function and greater dependence.